Bridged metallocene compounds as olefin-polymerization catalysts

ABSTRACT

The present invention relates to metallocene compounds consisting of indenyl-cyclopentadienyl groups non-symmetrically joined by a bivalent radical. Said compounds can be conveniently used as components of catalysts for the polymerization of olefins.

The present invention relates to bridged metallocene compounds, thecorresponding ligands, a process for their preparation and the use ofsaid compounds as components of catalysts for the polymerization ofolefins.

More specifically, the invention relates to metallocene compoundsconsisting of indenyl-cyclopentadienyl groups, non-symmetrically joinedby a bivalent radical.

It is known that metallocene compounds can be used in various reactionsof industrial interest.

For example, chiral, stereo rigid metallocene compounds consisting oftwo bridged indenyl groups and a metal such as zirconium, are known andused as components of catalysts for the polymerization of olefins and,in particular, for the preparation of stereo-regular polyolefins.

In these metallocenes, the indenyl groups are joined by means ofbivalent radicals which have two or more carbon atoms, such as —(CH₂)₂groups or with atoms different from carbon.

These radicals are generally bound in different positions relating tothe ring with five carbon atoms of both indenyl groups, as described inpatent applications EP-A-485,823, EP-A-372,414, WO 94/11406.

Metallocenes are also known, whose indenyl groups are joined by means ofbivalent radicals bound in position 4 of the ring with six carbon atomsof both indenyl groups, as described in patent applications EP 693 502,WO 96/38458.

New metallocene compounds have now been found in which the bivalentradical is bound to the ring with five carbon atoms of acyclopentadienyl, indenyl, fluorenyl group and to the ring with sixcarbon atoms of an indenyl group, which can be conveniently used ascomponents of catalysts for the polymerization of olefins.

An object of present invention relates, in particular, to metallocenecompounds having general formula (I):

wherein:

-   -   R₁ and R₂ can independently occupy any of the free positions of        the indene group;    -   R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ independently represent        hydrogen, halogen, preferably F, Cl or Br, a linear or branched,        saturated or unsaturated, cycloaliphatic or aromatic C₁–C₂₀        hydrocarbyl group, or a C₁–C₂₀ hydrocarbyl group substituted        with one or more halogen atoms, or a C₁–C₂₀ hydrocarbyl group        comprising one or more heteroatoms of groups 14 to 16 of the        periodic table of elements, preferably Si, O, N, S, P; in        addition, any two, or both pairs, of the substituents R₃, R₄, R₅        and R₆, adjacent to each other, are joined to each other to form        a saturated or unsaturated C₄–C₂₀ cyclic structure, comprising a        bond of the cyclopentadienyl ring, said structure optionally        containing one or more of the heteroatoms specified above;    -   M represents a metal selected from titanium, zirconium or        hafnium;    -   X₁ and X₂ each independently represent a group of an anionic        nature bound to the metal M.

Typical examples of X₁ and X₂ are hydride, halide, preferably chloride,a linear or branched alkyl group, such as methyl, ethyl, butyl,isopropyl, isoamyl, octyl decyl benzyl allyl, methyl-allyl, a cycloalkylgroup such as cyclopentyl, cyclohexyl, 4-methylcyclohexyl, an arylgroup, such as phenyl or toluyl, an alkoxyl or thioalkoxyl group, suchas methoxyl, ethoxyl, iso- or sec-butoxyl, ethylsulfide, a carboxylgroup, such as acetate, propionate, butyrate pivalate, versatate,naphthenate, or again, a dialkylamide group, such as diethylamide,dibutylamide, or an alkylsilylamide group, such asbis(trimethylsilyl)amide.

X₁ and X₂ can also be chemically bound to each other and form a cyclehaving from 4 to 7 different hydrogen atoms, also comprising the metalM.

Typical examples of this aspect are divalent anionic groups such as thetrimethylene or tetramethylene group, or the ethylenedioxy group.

The metallocene compounds of the present invention can exist inisomeric, racemic or meso forms.

A further object of the present invention relates to compounds havinggeneral formula (Ia) which are used for the preparation of the compoundshaving general formula (I):

wherein:

-   -   R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ have the meanings defined        above.

Examples of structures of compounds having general formula (Ia), areindicated in Table 1 below:

TABLE 1 Examples of structures of compounds with general formula

(I)

The compounds having general formula (Ia) can be prepared by means of asimple and original process which is illustrated in Scheme 1 below.

a =LiBu(₂eq.)/hexane; b=diethylcarbonate; c=PTSA/toluene; d=LiAlH₄ orLiR or RMgX; e=PBr; f=Li(C₅HR₃R₄R₅R₆)

In particular said process comprises the following steps:

-   -   (a) reaction of 1-indanol derivatives having formula (II),        wherein the R₁ and R₂ groups have the meaning defined above,        with LiBu to give the double salt having formula (III);    -   (b) reaction of the double lithium salt having for-is        mula (III), obtained in step (a), with electrophilic reagents,        as diethyl carbonate, to obtain hydroxy ester (IV);    -   (c) dehydration reaction of the alcohol function of the        hydroxyester having formula (IV), obtained in step    -   (b), carried out in an acid environment to give the ester (V);    -   (d) reduction reaction of the ester having formula (v), obtained        in step (c), to obtain the alcohol (VI);    -   (e) bromination reaction of the alcohol having formula (VI) to        give the bromine derivative (VII);    -   (f) formation reaction of the indenyl derivative having formula        (Ia), starting from the bromine derivative having formula (VII)        obtained in step (e) and from lithium salts of cyclopentadienyl        anions, whose corresponding neutral derivative can be        represented by the following general formula (VIII):        wherein each substituent R₃, R₄, R₅ and R₆ has the meanings        defined above.

Step (a) of the process of the present invention described in Chem. Ber.(1980) 113, 1304.

In particular, this article discloses that some benzyl alcohols andother phenyl carbinols, among which 1-indanol (Synthesis (1981) 59) canbe deprotonated in the presence of LiBu/tetramethylenediamine in pentaneto give lithium(ortho-lithium)alkoxides.

The reaction described in step (a) can be carried out in the presence ofbase reagents such as, for example, lithium butyl, lithium methyl,sodium hydride in hydrocarbon and/or ether solvents or their mixtures attemperatures ranging from −30° to 120° C.; the preferred conditionscomprise the use of lithium butyl in hexane at temperatures ranging from0° to 70° C.

Typical 1-indanols having general formula (II) are 1-indanol,2-methyl-1-indanol, 3-methyl-1-indanol, 3-ethyl-1-indanol,4-methyl-1-indanol.

One of the advantages of the process of the present invention consistsin the fact that many 1-indanol derivatives are available on the marketor can be easily prepared by means of well-known acylation/alkylationreactions of aromatic rings suitably substituted.

Step (b) of the process of the present invention comprises the reactionof the double lithium salt, having general formula (III), withelectrophilic reagents among which diethyl carbonate, dimethylcarbonate, carbon dioxide, ethyl chloroformiate, are particularlyappropriate for the purpose, in hydrocarbon and/or ether solvents ortheir mixtures at temperatures ranging from −100° to 120° C., preferablywith diethyl carbonate in hexane at temperatures ranging from −70° to25° C.

Step (c) of the process of the present invention consists in thedehydration of the hydroxy ester (IV) to obtain the correspondingindenyl derivative having general formula (V).

This reaction can be carried out in the presence of strong acids such asHCl, H₂SO₄, paratoluenesulfonic acid or blander dehydrating agents suchas, for example, silica gel.

The choice of solvent for this reaction is very wide as it is possibleto successfully use apolar solvents such as aliphatic hydrocarbons,medium polar solvents such as aromatic hydrocarbons or polar solventssuch as ethers or chlorinated hydrocarbons; the temperature at which thereaction can take place can also be selected within a very wide range,typically from 25° to 150° C. and the selection generally depends notonly on the substrate, but also on the type of solvent used, preferablyparatoluenesulfonic acid in toluene is used at temperatures ranging from50° to 110° C.

Step (d) of the process of the present invention comprises the reductionof the ester group to alcohol with the formation of the compound havinggeneral formula (VI); this reduction can be carried out with variousreagents among which LiAlH₄, NaBH₄, NaH, MgH₂, LiBu, LiMe, MeMgCl,PhMgBr, Bu^(t)MgCl, generally in ether solvents, but it is also possibleto use alternative solvents having other characteristics, attemperatures ranging from −70° to 100° C.; LiAl₄ in ethyl ether ispreferably used at temperatures ranging from −30° to 25° C.

Step (e) of the process of the present invention comprises thebromination of the alcohol function to give the bromine derivativehaving general formula (VII); also in this case there are varioussynthetic alternatives, well known to experts in the field, whichcomprise the use of various brominating agents in different solvents;the preferred conditions comprise the use of PBr₃ in methylene chlorideat temperatures ranging from −20° to 25° C.

Step (f) of the process of the present invention, comprises the reactionof a cyclopentadienyl anion with the bromine derivative having generalformula (VII), obtained by the reaction of the corresponding neutralderivative, having general formula (VIII), with a suitable base.

Experts in the field know that there is a wide variety of productscapable of satisfying this requirement; it is in fact possible to usealkyls or hydrides of electro-positive metals such as, for example,lithium methyl, lithium butyl, lithium ter-butyl, magnesium dibutyl,sodium hydride, potassium hydride, magnesium hydride, the well-knownGrignard reagents: RMgX, or also the alkaline or earth-alkaline metalsthemselves or their alloys.

All the reagents are generally easy to find on the market, withacceptable costs, and consequently their selection frequently depends onthe type of substrate whose anion is to be obtained.

The solvents for effecting this reaction can be selected from aliphaticor aromatic hydrocarbons, ethers and/or their mixtures, the preferenceof one or the other often depending on the particular demands ofsolubility or reaction rate of the case in question.

The temperatures at which the reaction is carried out can vary within avery wide range, typically from −80° to 110° C. and essentially dependon the thermal stability of the substrates and on the solvent used.

The preferred conditions for obtaining the anions of the compound havinggeneral formula (VIII) comprise the use of lithium butyl in mixtures ofhexane/THF at temperatures ranging from 0° to 60° C.

Typical compounds having general formula (VIII) are: cyclopentadiene,methyl-cyclopentadiene, tetramethyl-cyclopentadiene,trimethylsilyl-cyclopentadiene, indene, 3-meth-yl-indene,4,7-dimethyl-indene, 5,6dimethyl-indene, 4,5,6,7-tetrahydro-indene,4,5,6,710 tetrahydro-2-methyl-ind-ene, 2,4,5,6,7,8-hexahydro-azulene,2-methyl-2,4,5,6,7,8-hexahydro-azulene,4,5,6,7,8,9-hexahydro-2H-cyclopentacyc-lo-octene,4,5,6,7,8,9,10,11,12,13-decahydro-2H-cyclopen-tacyclododecene, fluorene,1,2,3,4,5,6,7,8-octa-hydro-fluo-rene.

In the preferred embodiment, the compound having general formula (VIII)is cyclopentadiene, tetramethyl-cyclopentadiene, indene,3-methyl-indene, 4,7dimethyl-indene, 2,4,5,6,7,8-hexahydro-azulene,fluo-rene.

In an even more preferred embodiment the compound having general formula(VIII) is indene, 4,7-dimethyl-indene.

This reaction can be carried out in a wide variety of solvents selectedfrom aromatic and/or aliphatic phatic hydrocarbons and from ethersand/or their mixtures, at a temperature ranging from −80° to 120° C.There are no particular limitations in the order of addition of thevarious reagents, but it is preferable to operate by adding the brominederivative (VII), either pure or diluted in ether solvent, to thesolution/suspension containing the cyclopentadienyl anion, obtained asdescribed above, at temperatures ranging from −70° to 25° C.

Alternatively, step (f) of the process of the present invention can becarried out by reacting the brominated product (VII) with a suitablelithium enolate giving rise to the formation of indenyl-cyclopentadienylproducts having general formula (XIII):

wherein:

-   -   R₁ and R₂ can independently occupy any of the free positions of        the indene group;    -   R₁, R₂, R₇, R₈, R₉, R₁₀ and R₁₁ independently represent        hydrogen, halogen, preferably F, Cl or Br, a linear or branched        C₁–C₂₀ hydrocarbyl group, saturated or unsaturated,        cycloaliphatic or aromatic, or a C₁–C₂₀ hydrocarbyl group        substituted with one or more halogen atoms, or a C₁–C₂₀        hydrocarbyl group comprising one or more heteroatoms of groups        14 to 16 of the periodic table of elements, preferably Si, O, N,        S, P, or, wherein any two of the substituents R₉, R₁₀ and R₁₁,        adjacent to each other, are joined to each other to form a        saturated or unsaturated C₄–C₂₀ cyclic structure, comprising a        bond of the cyclopentadienyl ring, said structure optionally        containing one or more of the heteroatoms specified above;    -   R₁₂ can be independently hydrogen, a linear or branched C₁–C₂₀        hydrocarbyl group, saturated or unsaturated, cycloaliphatic or        aromatic, or a C₁–C₂₀ hydrocarbyl group comprising one or more        heteroatoms of groups 14 to 16 of the periodic table of        elements, preferably Si, O, N, S, P.        The variant in step (f) of the process of the present invention        is indicated in Scheme 2:        g:Li[N(iso-Pr)₂/THF/−78° C, h: (VII)/THF;i:NaBH₄ or LiR₁₂ or        R₁₂MgX; 1: CuSO₄/toluene/110° C.

In accordance with this, a further object of the present inventionrelates to a variant of the process for the preparation of compoundshaving general formula (Ia), which gives rise to the formation ofanalogous products having general formula (XIII) wherein thesubstituents R₁, R₂, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ have the meaningdefined above, which comprises the following steps:

-   (g) reaction of a cyclic ketone, having general formula (IX),    wherein the groups R₉, R₁₀ and R₁₁, have the meaning defined above,    with a lithium amide to give the mixture of anions having general    formula (Xa)/(Xb);-   (h) reaction of the mixture of anions (Xa)/(Xb) with the brominated    product having general formula (VII), prepared according to what is    indicated above (Scheme 1);-   (i) reduction of the functional carbonyl group to alcohol, by means    of suitable reagents, with the formation of the derivative having    general formula (XII), wherein the R₁₂ group has the meaning defined    above;-   (1) dehydration of the derivative having general formula (XII),    obtained in step (i), with the formation of the desired    indenyl-cyclopentadienyl compound, having general formula (XIII),    wherein the groups R₁, R₂, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ have the    meaning defined above.

In step (g) a cyclic ketone having general formula (IX) is reacted witha strong non-alkylating base, in ether solvents such as ethyl ether,tetrahydrofuran, dioxane, as the dissolving capacity of the latter canimprove the reaction kinetics, but this does not mean that less polarsolvents, such as aromatic and/or aliphatic hydrocarbons, can also beconveniently used for the purpose, at temperatures ranging from −80° C.to 110° C., the selection of the latter depending on the type of solventand substrates used.

Typical strong bases, suitable for the purpose, are alcoholates ofalkaline and earth-alkaline metals such as for example lithiummethoxide, sodium methoxide, sodium ethoxide, sodium iso-propoxide,potassium ter-butoxide, magnesium di-ethoxide, etc. or the relativeamides such as, for example, lithium amide, sodium amide, lithiumdi-ethylamide, lithium diisopropylamide, lithiumbis-(trimethylsilyl)amide, potassium di-butylamide, etc.

In the preferred embodiment the strong bases are selected from lithiummethoxide, sodium ethoxide, potassium ter-butoxide, sodium amide,lithium diisopropylamide.

In an even more preferred embodiment the strong base is lithiumdi-isopropylamide.

Typical cyclic ketones having general formula (IX), suitable for beingused in step (g) of Scheme 2 are: cyclopent-1-en-3-one,1-methyl-cyclopent-1-en-3-one, 1,2,5-tri-methyl-cyclopent-1-en-3-one,indan-1-one, 3-methyl-indan-1-one, 4,7-dimethyl-indan-1-one,indan-2-one, etc.

In the preferred embodiment the cyclo-ketone compound having generalformula (IX) is selected from cyclopent-1-en-3-one,1,2,5-trimethylcyclopent-1-en-3-one, indan-1-one, 3-methyl-indan-1-one;in an even more preferred embodiment compound (IX) is indan-lone.

Step (h) of the process of the present invention consists in thereaction between the mixture of anions (Xa)/(Xb) with the brominatedproduct (VII), prepared according to Scheme 1, which can be carried outin hydrocarbon, ether solvents or their mixtures, the use of the samesolvent adopted in the previous step (g), at temperatures ranging from−80° C. to 70° C., normally being preferred.

In a preferred embodiment, the reaction is carried out in a mixture ofTHF/hexane at temperatures ranging from −70° to 25° C.

Step (i) of the process of the present invention consists in a reductionof the functional carbonyl group, present in the derivative havinggeneral formula (XI), to alcohol, with the formation of the compoundhaving general formula (XII). There are various possibilities, wellknown to experts in the field, for selecting the reducing reagentssuitable for the purpose, among which lithium aluminum hydride, sodiumboron hydride, sodium hydride, lithium methyl, lithium phenyl, ethylmagnesium bromide, isopropyl magnesium bromide, etc., which can besuccessfully used either in hydrocarbon or ether solvents or theirmixtures, at temperatures ranging from −40° to 70° C. In a preferredembodiment, sodium boron hydride in tetrahydrofuran is used attemperatures ranging from −20° to 25° C.

Step (1) of the process of the present invention, consists in thedehydration of the derivative (XII), obtained in step (i), to give thedesired indenyl-cyclopentadienyl product having general formula (XIII).

The latter can be carried out in the presence of dehydrating agents suchas, for example, silica gel, strong acids such as HCl, H₂SO₄,paratoluenesulfonic acid, or anhydrous inorganic salts such as, forexample, Cu (SO₄), Mg(SO₄), Na(SO₄)₂, CaCl₂, etc.

The selection of the solvent for this reaction is very wide as it ispossible to successfully use apolar solvents such as aliphatichydrocarbons, medium polar solvents such as aromatic hydrocarbons orpolar solvents such as ethers or chlorinated hydrocarbons; thetemperature at which the reaction takes place can also be selectedwithin a very wide range, typically from—20° to 130° C. and theselection generally depends not only on the substrate but also on thetype of solvent used. In a preferred embodiment anhydrous Cu (SO₄) isused in toluene at 110° C.

The processes of the present invention do not necessarily require theisolation of the single reaction products at the end of the respectivesteps.

In addition to the advantage of starting from products which are easilyavailable, the processes comprise quite simple chemical passages andproduce satisfactory overall yields.

The preparation of the complexes having general formula (I) can becarried out according to one of the well-known methods described inliterature for the production of bridged bis-cyclopentadienyl complexesof transition metals.

The method most commonly used comprises reacting a salt of the metal M(preferably a chloride), with a salt of an alkaline metal of the dianionof the bis-cyclo-pentadienyl ligand having the desired structure.

The preparation of the complexes having formula (I) normally comprisestwo steps, in the first of which the ligand having general formula (Ia)is reacted with a lithium alkyl, such as lithium methyl or lithiumbutyl, in an inert solvent, preferably consisting of an aromatichydrocarbon or an ether, particularly tetrahydrofuran or ethyl ether.

The temperature during the reaction is preferably maintained below roomtemperature to avoid the creation of secondary reactions. At the end ofthe reaction the corresponding lithium salt of the cyclopentadienyldianion is obtained.

In the second step, the salt of the cyclopentadienyl dianion is reactedwith a salt, preferably a chloride, of the transition metal M, again inan inert organic solvent at a temperature preferably ranging from −30°to 70° C.

At the end of the reaction, the complex having formula (I) thus obtainedis separated and purified according to the known methods oforganometallic chemistry.

As is known to experts in the field, the above operations are sensitiveto the presence of air and humidity and should therefore be carried outin an inert atmosphere, preferably under nitrogen or argon.

Numerous general and specific methods which substantially originate fromthe method indicated above, are described in literature, such as, forexample in the publications of D. J. Cardin “Chemistry of Organo Zr andHf Compounds” J. Wiley and Sons Ed., New York (1986); R. Haltermann“Chemical Review”, vol. 92 (1992) pages 965–994; R. O. Duthaler and A.Hafner “Chemical Review”, vol. 92 (1992) pages 807–832.

The metallocene compounds of the present invention can be convenientlyused as catalytic components for the polymerization of olefins.

A further object of the present invention therefore relates to acatalyst for the polymerization of olefins comprising the reactionproduct between:

-   (A) a metallocene compound having formula (I) obtained as described    above, and-   (B) one or more compounds capable of activating the metallocene (I)    selected from those known in the art, particularly an organic    derivative of an element M′ different from carbon and selected from    the elements of groups 1, 2, 12, 13 and 14 of the periodic table.

In particular, according to the present invention, said element M′ isselected from boron, aluminum, zinc, magnesium, gallium and tin, moreparticularly boron and aluminum.

In a preferred embodiment of the present invention, the component (B) isan organo-oxygenated derivative of aluminum, gallium or tin. This can bedefined as an organic compound of M′, in which the latter is bound to atleast one oxygen atom and to at least one organic group consisting of analkyl group having from 1 to 12 carbon atoms, preferably methyl.

According to this aspect of the invention, component (B) is morepreferably an aluminoxane. As is known, aluminoxanes are compoundscontaining Al—O—Al bonds, with a varying O/Al ratio, which can beobtained, under controlled conditions, by the reaction of an aluminumalkyl or aluminum alkyl halide, with water or other compounds containingpre-established quantities of water available, such as, for example, inthe case of the reaction of aluminum trimethyl with aluminum sulfatehexahydrate, copper sulfate pentahydrate or iron sulfate pentahydrate.

Aluminoxanes preferably used for the formation of the polymerizationcatalyst of the present invention are oligo- poly-meric, cyclic and/orlinear compounds, characterized by the presence of repetitive unitshaving the following formula:

wherein R₁₃ is a C₁–C₁₂ alkyl group, preferably methyl.

Each dialuminoxane molecule preferably contains from 4 to 70 repetitiveunits which may also not all be equal to each other, but containdifferent R₁₃ groups.

When used for the formation of a polymerization catalyst according tothe present invention, the aluminoxanes are put in contact with acomplex having formula (I) in such proportions that the atomic ratiobetween Al and the transition metal M is within the range of 10 to 10000and preferably from 100 to 5000. The sequence with which the complex (I)and the aluminoxane are put in contact with each other, is notparticularly critical.

In addition to the above aluminoxanes, the definition of component (B)according to the present invention also comprises galloxanes (in which,in the previous formulae, gallium is present instead of aluminum) andstannoxanes, whose use as cocatalysts for the polymerization of olefinsin the presence of metallocene complexes is known, for example, frompatents U.S. Pat. No. 5,128,295 and U.S. Pat. No. 5,258,475.

According to another preferred aspect of the present invention, saidcatalyst can be obtained by putting component (A) consisting of at leaston complex having formula (I), in contact with component (B) consistingof at least one compound or a mixture of organometallic compounds of M′capable of reacting with the complex having formula (I), extracting fromthis a σ-bound group R′ to form, on the one hand at least one neutralcompound, and on the other hand an ionic compound consisting of ametallocene cation containing the metal M and an organicnon-coordinating anion containing the metal M′, whose negative charge isdelocalized on a multicenter structure.

Components (B) suitable as ionizing systems of the above type arepreferably selected from the voluminous organic compounds of boron andaluminum, such as for example, those represented by the followinggeneral formulae:[(R_(C))_(x)NH_(4-x)]⁺[B(R_(D))₄]⁻; B(R_(D))₃; [Ph₃C]⁺[B(R_(D))₄]⁻;[(R_(C))₃PH]⁺[B(R_(D))₄]⁻; [Li]⁺[B(R_(D))₄]⁻; [Li]⁺[A1(R_(D))₄]³¹ ;wherein the deponent “x” is an integer ranging from 0 to 3, each R_(c)group independently represents an alkyl or aryl radical having from 1 to12 carbon atoms and each RD group independently represents an arylradical partially or, preferably, totally fluorinated, having from 6 to20 carbon atoms.

Said compounds are generally used in such quantities that the ratiobetween the atom M′ of component (B) and the atom M of component (A) iswithin the range of 0.1 to 15, preferably from 0.5 to 10, morepreferably from 1 to 6.

Component (B) can consist of a single compound, normally an ioniccompound, or a combination of this compound with MAO, or, preferably,with an aluminum trialkyl having from 1 to 16 carbon atoms in each alkylresidue, such as for example ALMe₃, AlEt₃, Al(i-Bu)₃.

In general, the formation of the ionic metallocene catalyst, inaccordance with the present invention, is preferably carried out in aninert liquid medium, more preferably hydrocarbon. The selection ofcomponents (A) and (B) which are preferably combined with each other, aswell as the particular method used, can vary depending on the molecularstructures and result desired, according to what is described in detailin specific literature available to experts in the field.

Examples of these methods are qualitatively schematized in the listprovided hereunder, which however does not limit the overall scope ofthe present invention:

-   (i) by contact of a metallocene having general formula (I) wherein    at least one, preferably both, of the substituents X₁ and X₂ is    hydrogen or an alkyl radical, with an ionic compound whose cation is    capable of reacting with one of the substituents X₁ or X₂ to form a    neutral compound, and whose anion is voluminous, non-coordinating    and capable of delocalizing the negative charge;-   (ii) by the reaction of a metallocene having the previous    formula (I) with an alkylating agent, preferably an aluminum    trialkyl, used in molar excess of 10/1 to 500/1, followed by the    reaction of a strong Lewis acid, such as for example,    tris(pentafluo-rophenyl)boron a in more or less stoichiometric    quantity or in slight excess with respect to the metal M;-   (iii) by contact and reaction of a metallocene having the previous    formula (I) with a molar excess of 10/1 to 1000/1, preferably from    30/1 to 500/1 of an aluminum trialkyl or an alkylaluminum halide or    one of their mixtures, which can be represented by the formula    AlR_(m)X_(3-m), wherein R is a linear or branched C₁–C₁₂ alkyl    group, X is a halogen, preferably chlorine or bromine, and “m” is a    decimal number ranging from 1 to 3; followed by the addition to the    composition thus obtained, of at least an ionic compound of the type    described above in such quantities that the ratio between B or Al    and the atom M in the metallocene complex is within the range of 0.1    to 20, preferably from 1 to 6.    Examples of ionizing ionic compounds or multicomponent reactive    systems capable of producing an ionic catalytic system by reaction    with a metallocene complex, according to the present invention, are    described in the following patent publications, whose content in    herein incorporated as reference:    -   European patent application, published under the Nr.: EP-A        277,003, EP-A 277,004, EP-A 522,581, EP-A 495,375, EP-A 520,732,        EP-A 478,913, EP-A 468,651, EP-A 427,697, EP-A 421,659, EP-A        418,044;    -   International patent applications published under the Nr.: WO        92/00333, WO 92/05208; WO 91/09882;    -   Patents U.S. Pat. No. 5,064,802, U.S. Pat. No. 2,827,446, U.S.        Pat. No. 5,066,739.

Also included in the scope of the present invention are those catalystscomprising two or more complexes having formula (I) mixed with eachother. Catalysts of the present invention based on mixtures of complexeshaving different catalytic activities can be advantageously used inpolymerization when a wider molecular weight distribution of thepolyolefins thus produced is desired.

According to an aspect of the present invention, in order to producesolid components for the formation of catalysts for the polymerizationof olefins, the above complexes can also be supported on inert solids,preferably consisting of oxides of Si and/or Al, such as for example,silica, alumina or silica-aluminates.

For the supporting of said catalysts, the known supporting techniquescan be used, normally comprising contact, in a suitable inert liquidmedium, between the carrier, optionally activated by heating totemperatures exceeding 200° C., and one or both of components (A) and(B) of the catalyst of the present invention. For the purposes of thepresent invention, it is not necessary for both components to besupported, as it is also possible for only the complex having formula(I) or the organic compound of B, Al, Ga or Sn as defined above, to bepresent on the surface of the carrier. In the latter case, the componentwhich is not present on the surface is subsequently put in contact withthe supported component, at the moment of the formation of the catalystactive for the polymerization.

Also included in the scope of the present invention are the complexes,and catalytic systems based on these, which have been supported on asolid by means of the functionalization of the latter and formation of acovalent bond between the solid and a metallocene complex included informula (I) above.

A particular method for the formation of a supported catalyst accordingto the present invention comprises pre-polymerizing a relatively smallfraction of monomer or mixture of monomers in the presence of thecatalyst, so as to include this in a solid microparticulate, which isthen fed to the actual reactor itself for completing the process in thepresence of an additional olefin(s). This provides a better control ofthe morphology and dimensions of the polymeric particulate obtained atthe end.

One or more other additives or components can be optionally added to thecatalyst according to the present invention, as well as the twocomponents (A) and (B), to obtain a catalytic system suitable forsatisfying specific requisites. The catalytic systems thus obtainedshould be considered as being included in the scope of the presentinvention. Additives or components which can be included in thepreparation and/or formulation of the catalyst of the present inventionare inert solvents such as, for example, aliphatic and/or aromatichydrocarbons, aliphatic and aromatic ethers, weakly co-ordinatingadditives (Lewis bases) selected, for example, from non-polymerizableolefins, ethers, tertiary amines and alcohols, halogenating agents suchas silicon halides, halogenated hydrocarbons, preferably chlorinated,and the like, and again all other possible components normally used inthe art for the preparation of the traditional homogeneous catalysts ofthe metallocene type for the (co)polymerization of olefins.

Components (A) and (B) form the catalyst of the present invention bycontact with each other, preferably at temperatures ranging from 20° to60° C. and for times varying from 10 seconds to 1 hour, more preferablyfrom 30 seconds to 15 minutes.

The catalysts according to the present invention can be used withexcellent results in substantially all known (co)polymerizationprocesses of olefins, either in continuous or batchwise, in one or moresteps, such as, for example, processes at low (0.1–1.0 MPa), medium(1.0–10 MPa) or high (10–150 MPa) pressure, at temperatures ranging from10° to 240° C., optionally in the presence of an inert diluent. Hydrogencan be conveniently used as molecular weight regulator.

These processes can be carried out in solution or suspension in a liquiddiluent normally consisting of an aliphatic or cycloaliphatic saturatedhydrocarbon, having from 3 to 20 carbon atoms or a mixture of two ormore of these, but which can also consist of a monomer as, for example,in the known co-polymerization polymerization process of ethylene andpropylene in liquid propylene. The quantity of catalyst introduced intothe polymerization mixture is preferably selected so that theconcentration of the metal M ranges from 10⁻⁴ to 10⁻⁸ moles/liter.

Alternatively, the polymerization can be carried out in gas phase, forexample, in a fluid bed reactor, normally at pressures ranging from 0.5to 5 MPa and at temperatures ranging from 50 to 150° C.

According to a particular aspect of the present invention, the catalystfor the (co)polymerization of ethylene with other olefins is preparedseparately (preformed) by contact of components (A) and (B), and issubsequently introduced into the polymerization environment.

The catalyst can be first charged into the polymerization reactor,followed by the reagent mixture containing the olefin or mixture ofolefins to be polymerized, or the catalyst can be charged into thereactor already containing the reagent mixture, or finally, the reagentmixture and the catalyst can be contemporaneously fed into the reactor.

According to another aspect of the present invention, the catalyst isformed “in situ”, for example by introducing components (A) and (B)separately into the polymerization reactor containing the pre-selectedolefinic monomers.

The catalysts according to the present invention can be used withexcellent results in the polymerization of ethylene to give linearpolyethylene and in the copolymerization of ethylene with propylene orhigher olefins, preferably having from 4 to 12 carbon atoms, to givecopolymers having different characteristics depending on the specificpolymerization conditions and on the quantity and structure of thecomonomer used.

For example, linear polyethylenes can be obtained, with a densityranging from 0.880 to 0.940, and with molecular weights ranging from10,000 to 2,000,000. The olefins preferably used as comonomers ofethylene in the production of low or medium density linear polyethylene(known with the abbreviations ULDPE, VLDPE and LLDPE depending on thedensity), are 1-butene, 1-hexene and 1-octene.

The catalyst of the present invention can also be conveniently used incopolymerization processes of ethylene and propylene to give saturatedelastomeric copolymers vulcanizable by means of peroxides and extremelyresistant to aging and degradation, or in the terpolymerization ofethylene, propylene and a diene, generally non-conjugated, having from 4to 20 carbon atoms, to obtain vulcanizable rubbers of the EPDM type.

In the case of these latter processes, it has been found that thecatalysts of the present invention allow the production of polymershaving a particularly high comonomer content and average molecularweight under the polymerization conditions.

In the case of the preparation of EPDM, the dienes which can be used forthe purpose are preferably selected from:

-   -   linear chain dienes such as 1,4-hexadiene and 1,6-octadiene;    -   branched dienes such as 5-methyl-1,4-hexadiene;        3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene;    -   dienes with a single ring such as 1,4cyclohexadiene;        1,5-cyclo-octadiene; 1,5-cyclododecadiene;    -   dienes having bridged condensed rings such as dicyclopentadiene;        bicyclo[2.2.1]hepta-2,5-diene; alchenyl, alkylidene,        cycloalkenyl and cycloalky-lidene norbornenes such as        5-methylene-2norbornene, 5-ethylidene-2-borbornene (ENB),        5-propenyl-2-norbornene.

Among the non-conjugated dienes typically used for preparing thesecopolymers, dienes containing at least one double bond in a stretchedring are preferred, even more preferably 5-ethylidene-2-norbornene(ENB), and also 1,4-hexadiene and 1,6-octadiene.

In the case of EPDM terpolymers, it is convenient for the quantity ofdienic monomer not to exceed 15% by weight, and it is preferably from 2to 10% by weight. The propylene content on the other hand ranges from 20to 55% by weight.

The catalysts of the present invention can also be used in homo- andco-polymerization processes of olefins according to the knowntechniques, giving, with excellent yields, atactic, isotactic orsyndiotactic polymers, depending on the structure and geometry of themetallocene complex having formula (I).

Olefins suitable for the purpose are those having from 3 to 20 carbonatoms, optionally also comprising halogens and/or other heteroatoms oraromatic nuclei such as, for example, propylene, 1-butene, 1-hexene,1-octene, 4-methyl-1-pentene, 1-decene and styrene.

The present invention is further described by the following examples,which, however, are provided for purely illustrative purposes and do notlimit the overall scope of the invention itself.

Characterization Methods

The analytical techniques and characterization methods used in theexamples are listed below and are briefly described.

The characterization by means of NMR spectroscopy mentioned in thefollowing examples was carried out on a nuclear magnetic resonancespectrometer mod. Bruker MSL-300, using, unless otherwise specified,CDCl₃ as solvent for each sample.

The molecular weight measurement of the olefinic polymers was carriedout by means of Gel-Permeation Chromatography (GPC). The analyses of thesamples were effected in 1,2,4-trichlorobenzene (stabilized withSantonox) at 135° C. with a WATERS 150-CV chromatograph using a Watersdifferential refractometer as detector. The chromatographic separationwas obtained with a set of μ-Styragel HT columns (Waters) of which threewith pore dimensions of 10³, 10⁴, 10⁵ Å respectively, and two with poredimensions of 10⁶ Å, establishing a flow-rate of the eluant of 1 ml/min.The data were obtained and processed by means of Maxima 820 softwareversion 3.30 (Millipore); the number (M_(n)) and weight (M_(w)) averagemolecular weight calculation was carried out by universal calibration,selecting polystyrene standards with molecular weights within the rangeof 6,500,000–2,000, for the calibration.

The determination of the content of units deriving from propylene andpossible diene in the polymers is carried out (according to the methodof the Applicant) by means of IR on the same polymers in the form offilms having a thickness of 0.2 mm, using an FTIR Perkin-Elmerspectrophotometer model 1760. The intensity of the characteristic peaksis measured, of propylene at 4390 cm⁻¹ and ENB at 1688 cm⁻¹respectively, in relation to the peak at 4255 cm⁻¹, and the quantity isdetermined using a standard calibration curve.

The Melt Flow Index (MFI) of the polymers is determined in accordancewith the regulation ASTM D-1238 D.

The Mooney viscosity (1+4) is determined at 100° C. using a Monsanto“1500 S” viscometer according to the method ASTM D 1646/68.

EXAMPLE 1 Synthesis of 1-methyl-4-methylene(1-indenyl)indene

The following products are reacted:

-   170 ml of benzene-   22.7 g (264 mmoles) of crotonic acid-   106 g (795.2 mmoles) of aluminum trichloride

The solution of crotonic acid in 100 ml of benzene is added dropwise tothe suspension of AlCl₃ in 70 ml of benzene. The mixture is stirred at80° C. for 5 hours. It is poured into ice and is extracted with ethylether. After washing until neutrality with a saturated aqueous solutionof NaHCO₃ and water and anhydrifying on Na₂SO₄, the solvent isevaporated. The product is purified by distillation (T_(boil.)=125° C.).32.0 g are obtained (yield=83%).

32.0 g (219.2 mmoles) of 3-methyl-1-indanone, obtained in the previousstep, are reacted with:

-   5.6 g (147 mmoles) of sodium boronhydride-   128 ml of tetrahydrofuran-   64 ml of methanol

NaBH₄ is added, in portions, to the solution of 3methyl-1-indanone intetrahydrofuran and methanol, at 0° C. After 2 hours the mixture ispoured into ice and is extracted with ethyl ether. After washing theorganic extracts to neutrality with a saturated solution of NaCl andanhydrifying on Na₂SO₄, the mixture is filtered and the solventevaporated. 30.8 g of product are obtained (95%).

14.8 g (0.1 moles) of 3-methyl-1-indanol, obtained in the previous step,are reacted with:

-   80 ml (0.2 moles) of LiBu 2.5 M in hexane-   26.7 ml (0.22 moles) of diethylcarbonate-   500 ml of hexane

N-butyl lithium is added, by means of a drip funnel, over a period ofabout 1 h, in an inert atmosphere, to the suspension of3-methyl-1-indanol in hexane, at 20° C. At the end of the addition thereaction mixture is heated to 60° C. for 2 h, and, after cooling to −70°C., diethyl carbonate is then added. The temperature is left to riseslowly to 25° C. and, after a further 8 h, the reaction mass is pouredinto water and is extracted with ethyl ether. The separated organicphase is washed with water until neutrality, anhydrified on sodiumsulfate and the solvent is evaporated at reduced pressure. Afterpurification on a silica gel column (eluant: hexane/ethyl acetate 9/1),5.6 g of 3-methyl-7-carboethoxy-1-indanol are obtained.

-   5.6 g (25.45 mmoles) of 3-methyl-7-carboethoxy-1-indanol-   80 ml of toluene-   0.1 g (0.58 mmoles) of p-toluenesulfonic acid (PTSA)

Para-toluenesulfonic acid is added to the solution of3-methyl-7-carboethoxy-1-indanol in toluene. The mixture is heated to100° C. and the water is removed by azeotropic distillation. After 2 h asaturated aqueous solution of NaHCO₃ is added, the organic phase isseparated, washed with water until neutrality and anhydrified on NaSO₄.Finally the solvent is removed at reduced pressure and, afterpurification on a silica gel column (eluant: hexane/ethyl acetate 95/5),

-   5.0 g of 3-methyl-7-carboethoxy-1-indene are obtained.-   5.0 g (24.7 mmoles) of 3-methyl-7-carboethoxy-1-indene-   0.6 g (15.8 mmoles) of LiAlH₄-   100 ml of ethyl ether

A solution of 3-methyl-7-carboethoxy-1-indene in 40 ml of ethyl etherare added, at −30° C., to the suspension of LiAlH₄ in 60 ml of ethylether. The temperature is slowly left to rise to 25° C. and after 30 minwater is slowly added and the mixture is acidified with HCl 2M. Thereaction mass is extracted with ethyl ether, washed repeatedly withwater until neutrality and dried on NaSO₄. The solvent is finallyremoved under vacuum and 3.76 g of 7-(3-methylindenyl)methanol areobtained.

-   3.76 g (23.5 mmoles) of 7-(3-methylindenyl)methanol-   2.1 g (7.86 mmoles) of PBr₃-   50 ml of methylene chloride

Phosphorous tribromide is slowly added, by means of a drip funnel, tothe solution of 7-(3methylindenyl)methanol in CH₂Cl₂, cooled to −20° C.The temperature is left to rise to 25° C. and after 30 min a saturatedaqueous solution of NaHCO₃ is slowly added. The reaction mass isextracted various times with ethyl ether, the organic extracts arewashed with water until neutrality and dried on NaSO₄. After removingthe solvent at reduced pressure, 4.9 g of 4bromomethyl-1-methylindeneare obtained.

-   7 g (31.4 mmoles) of 4-bromomethyl-1-methylindene, obtained in the    previous step, are reacted with:-   31 ml (77.5 mmoles) of LiBu 2.5 M in hexane-   200 ml of THF-   7.3 ml (62.3 mmoles) of indene

Butyl lithium is added dropwise to the solution of indene in 100 ml ofTHF. The mixture is left under stirring for 2 h at room temperature andis then cooled to −70° C. Bromine dissolved in THF is added. After 1 hat this temperature the mixture is left to rise to room temperature andis poured into water. It is extracted with ethyl ether, the extracts arewashed until neutrality and are anhydrified on sodium sulfate. Theresidue obtained by evaporation of the solvent is purified on a silicagel column using petroleum ether as eluant. In this way 4.3 g of1-methyl-4-methylene (1-indenyl)indene are obtained (53% yield).

EXAMPLE 2 Synthesis of 4-methylene(1-indenyl)indene

The following products are reacted:

-   16.0 g (119.4 mmoles) of 1-indanol-   100 ml (250 mmoles) of LiBu 2.5 M in hexane-   31.5 (259.6 mmoles) of diethylcarbonate-   500 ml of hexane

N-butyl-lithium is added dropwise to the suspension in 1-indanol inhexane, at −5° C. The mixture is stirred at 60° C. for 2 hours anddiethylcarbonate is added, at −70° C. The mixture is left to rise toroom temperature. After 8 hours, it is poured into water and extractedwith ethyl ether. After washing the organic extracts to neutrality andanhydrifying on Na₂SO₄, the solvent is evaporated under vacuum. Theproduct is purified by chromatographic separation on silica gel eluatingwith hexane and ethyl acetate in a ratio of 95/5. 6 g of product areobtained (yield=24.5%).

5 g (24.3 mmoles) of hydroxy-ester, obtained in the previous step, arereacted with:

-   200 mg (1.05 mmoles) of para-toluenesulfonic acid-   20 ml of toluene

The toluene solution of hydroxy ester and PTSA are stirred at 90° C. for3 hours. The mixture is washed, until neutrality, with a saturatedaqueous solution of NaHCO₃ and with water. After anhydrifying theorganic phase on Na₂SO₄ and filtering, the solvent is evaporated. Theresidue is purified on a silica gel chromatographic column with hexaneand ethyl acetate as eluant in a ratio of 95/5. 4.0 g of ester are thusobtained (yield 87.7%).

8.8 g (46.8 mmoles) of ester, obtained in the previous step, are reactedwith:

-   2.1 g (55.3 mmoles) of lithium aluminum hydride-   120 ml of ethyl ether.

The ester dissolved in 20 ml of ethyl ether is added, at −20° C. to thesuspension, in ethyl ether, of LiAlH₄. After 6 hours water is slowlyadded, the mixture is acidified with HCl (2N) and extracted with ethylether. After washing the organic extracts to neutrality and anhydrifyingon Na₂SO₄, the mixture is filtered and the solvent evaporated. 6.6 g ofalcohol are obtained (yield 96%).

6.6 g (45.2 mmoles) of alcohol, obtained in the previous step, arereacted with:

-   1.5 ml (15.82 mmoles) of phosphorous tribromide-   70 ml of methylene chloride

The phosphorous tribromide is added dropwise to the solution, inmethylene chloride, of alcohol at −20° C. After 1 hour a saturatedaqueous solution of NaHCO₃ is added dropwise and the mixture isextracted several times with ethyl ether. After washing the organicextracts to neutrality and anhydrifying on Na₂SO₄, the mixture isfiltered and the solvent evaporated. 5.0 g of 4-bromomethyl-indene areobtained (yield 53%).

-   4.44 ml (33.6 mmoles) of indene-   15 ml (33.6 mmoles) of LiBu solution 2.5 M in hexane-   5 g (24 mmoles) of 4-bromomethyl-indene-   90 ml of tetrahydrofuran-   45 ml of hexane

N-butyl-lithium is added, at 5° C, to the solution, in THF in hexane, ofindene. After 1 hour, the mixture is cooled to −70° C. and benzylbromide dissolved in 20 ml of THF is added. The mixture is left to riseto room temperature. After 8 hours, it is poured into water and isextracted with ethyl ether. After washing the ether extracts toneutrality with water and anhydrifying on Na₂SO₄, the mixture isfiltered and the solvent evaporated.

After purification on a silica gel chromatographic column (eluant:hexane), 2.3 g of 4-methylene(1-indenyl) indene are obtained (yield39.3%)

EXAMPLE 3 Synthesis of7-methyl-4-methylene(4,7-dimethyl-1indenyl)-indene

The following reaction scheme is followed:

-   108.0 g (583.7 mmoles) of o-methylbenzylbromide-   150 ml (988 mmoles) of dimethylmalonate-   21.4 g (930 mmoles) of sodium-   350 ml of ethyl alcohol-   25 g (445 mmoles) of KOH-   30 ml of thionyl chloride-   38 g (285.7 mmoles) of aluminum trichloride

Metal sodium is added, in portions, to the ethanol. Diethylmalonate isslowly added dropwise to the solution of sodium ethylate in ethanol, at50° C., and then o-methyl-benzylbromide is added rapidly. The mixture iskept under stirring at boiling point for 2 hours. After evaporating mostof the ethanol, the mixture is poured into water and is extracted withethyl ether; after anhydrifying on Na₂SO₄, the solvent is evaporated atreduced pressure. The product is purified by means of distillation(T=125° C.; P=1 mmHg). 50 g of monosubstituted diethylmalonate are thusobtained.

50 g of monosubstituted diethylmalonate dissolved in 75 ml of ethanolare added to the solution of KOH in 75 ml of water. The mixture isstirred for 4 hours at 80° C. After removing the ethanol by evaporationat reduced pressure, the mixture is acidified with HCl (1:1) andextracted with ethyl acetate. After washing the organic extracts toneutrality and anhydrifying on Na₂SO₄, the solvent is evaporated undervacuum. 37.4 g of monosubstituted malonic acid are obtained.

The diacid, thus obtained, decarboxylates in 1 hour, at 160° C. 31.6 gof mono-acid are obtained.

SOCl₂ is added to the acid, dropwise. The mixture is stirred for 12hours. The acyl chloride is isolated after removing the excess thionylchloride by means of distillation under vacuum. 31.0 g of acyl chlorideare obtained.

The acyl chloride dissolved in 50 ml of methylene chloride is added, at10° C., to the suspension of AlCl₃ in 400 ml of methylene chloride. Themixture is stirred for 1 hour at room temperature. It is poured into iceand extracted with ethyl ether. After washing the organic extracts toneutrality and anhydrifying on Na₂SO₄, the solvent is evaporated undervacuum. 22.0 g of product are obtained (total yield=26%).

-   22.0 g (150.7 mmoles) of 4-methyl-1-indanone-   3.9 g (102.6 mmoles) of sodium boronhydride-   88 ml of tetrahydrofuran-   44 ml of methanol

NaBH₄ is added, in portions, at 0° C., to the solution of4-methyl-1-indanone in THF/CH₃OH. After 3 hours the mixture is pouredinto water and extracted with ether. After washing the organic extractsto neutrality and anhydrifying on Na₂SO₄, the solvent is evaporatedunder vacuum. 22.0 g of 4-methyl-1-indanol are obtained (yield=99%).

-   22 g (148.6 mmoles) of 4-methyl-1-indanol-   123 ml (307 mmoles) of n-butyl-lithium 2.5 M solution in hexane-   750 ml of hexane-   39.1 ml (322 mmoles) of diethylcarbonate

N-butyl-lithium is added, at 0° C., to the solution of4-methyl-1-indanol in hexane. The mixture is stirred for 2 hours at 60°C. Diethylcarbonate is added dropwise, at −70° C. The mixture is left torise to room temperature. After 8 hours it is poured into water andextracted with ethyl ether. After washing the organic extracts toneutrality and anhydrifying on Na₂SO₄, the solvent is evaporated. Afterpurification on a silica gel chromatographic column (eluant hexane/ethylacetate=9/1), 6.9 g of product are obtained (yield=21.2%)

-   12.5 g (56.8 mmoles) of hydroxy ester-   400 mg (2.1 mmoles) of p-toluenesulfonic acid (PTSA)-   100 of toluene.

PTSA is added to the toluene solution of hydroxy ester. The mixture isstirred at boiling point, removing the azeotropic mixture/toluene bydistillation. After 2 hours the mixture is washed until neutrality witha saturated solution of NaHCO₃ and anhydrified on Na₂SO₄, and thesolvent is evaporated. 10.0 g of product are thus obtained (yield=87%).

-   10.0 g (49.5 mmoles) of ester-   1.1 g (28.9 mmoles) of lithium aluminum hydride-   200 ml of ethyl ether

The ester dissolved in 60 ml of ethyl ether is added, at −30° C., bymeans of a drip funnel, to the suspension in ethyl ether of LiAlH₄.After 30 minutes water is slowly added, at 0° C., and then HCl (2N); themixture is extracted with ethyl ether. After washing the organicextracts to neutrality and anhydrifying on Na₂SO₄, the solvent isevaporated at reduced pressure.

-   7.8 g of alcohol are obtained (yield=99%).-   8.8 g (55 mmoles) of alcohol-   1.77 ml (18.15 mmoles) of phosphorous tribromide-   110 ml of methylene chloride.

PBr₃ is added dropwise, at −20° C., to the solution of alcohol inCH₂Cl₂. After 30 minutes a saturated aqueous solution of NaHCO₃ isslowly added until basic pH. The mixture is extracted with ethyl etherand is washed to neutrality with water. After anhydrifying on Na₂SO₄ andevaporating the solvent, 7.8 g of product are obtained (yield=64%).

Preparation of 4,7-dimethyl-indenyl-lithium

-   14.5 g (137 mmoles) of p-xylene-   16 g of AlCl₃-   10 ml (104.7 mmoles) of 3-chloropropionyl chloride-   70 ml of methylene chloride-   90 ml of conc. H₂SO₄.

A solution of 3-chloro propionyl chloride in xylene is dripped in about1 hour into a suspension of AlCl₃ in methylene chloride maintained at 0°C. in an inert atmosphere. At the end of the addition the mixture isleft to rise to 10° C. and is maintained at 10–20° C. for about 2 hours.It is poured into ice and extracted with methylene chloride. The organicextracts are washed with water until neutrality and then dried on sodiumsulfate.

The residue obtained by evaporation of the solvent is added to H₂SO₄ atsuch a rate as to maintain the temperature between 20 and 30° C. At theend of the addition the mixture is brought to 80° C. and maintained atthis temperature for 2 hours. The mixture is then poured into ice and isextracted with ethyl ether. ether solution is washed to neutrality witha saturated solution of sodium bicarbonate and then water, and is driedon sodium sulfate. The solid obtained by evaporation of the ether iswashed with petroleum ether and dried. 20 g of 4,7-dimethyl-1-indanoneare thus obtained (91% of yield in the two passages).

-   2.9 g (18.1 mmoles) of 4,7-dimethyl-1-indanone-   0.35 g (9.2 mmoles) of LiAlH₄-   30 ml of ethyl ether-   10 ml of THF-   0.2 g (1.05 mmoles) of p-toluenesulfonic acid (PTSA).    Indanone is slowly added to the suspension of LiAlH₄ maintained at    −30° C. in an inert atmosphere. After 30 minutes the reaction is    completed. Ice and HCl 2N are carefully added, the mixture is then    extracted with ethyl ether and washed to neutrality, dried on sodium    sulfate and evaporated. The indanol obtained is dissolved in 10 ml    of THF, p-toluenesulfonic acid is added and the mixture is brought    to reflux temperature for 1 hour. Solid NaHCO₃ and Na₂SO₄ are added.    The mixture is filtered and the solvent evaporated obtaining 2.4 g    of 4,7-dimethylindene (91% yield).-   7.4 g (51.4 mmoles) of 4,7-dimethyl-indene-   32.3 ml (51.6 mmoles) of LiBu 1.6 M solution in hexane-   7.8 g (35.1 mmoles) of benzyl bromide-   297 ml of tetrahydrofuran-   148 ml of hexane

LiBu is added to the solution in THF and hexane of 4,7-dimethyl-indene.After 2 hours, the bromide dissolved in 20 ml of THF and 10 ml of hexaneis added, at −70° C. The mixture is left to rise to room temperature,after 8 hours water is added and the mixture is extracted with ethylether. After washing the organic extracts to neutrality and anhydrifyingon Na₂SO₄, the solvent is evaporated. 3.1 g of product are obtained,after purification on a silica gel column using hexane/ethyl acetate aseluant in a ratio of 98/2 (yield=31%).

EXAMPLE 4 Synthesis of 4-methylene(2-indenyl)indene

-   11.2 ml (79.8 mmoles) of diisopropylamine-   29 ml (72.5 mmoles) of LiBu 2.5 M solution in hexane-   9.5 g (72 mmoles) of 1-indanone-   6.0 g (28.8 mmoles) of 4-bromethylindene

LiBu is added dropwise to the solution of diisopropylamine in 70 ml ofTHF, at −20° C. After 40 minutes a 2 M solution of 1-indanone in THF isadded, at −70° C. After 90 minutes a 2 M solution of 4-bromoethylindene(prepared as described in example 2) in THF is added. The mixture isleft to rise to room temperature. After 30 minutes it is poured intowater and extracted with ethyl ether. After washing the organic extractsto neutrality, with a saturated aqueous solution of NH₄Cl and withwater, they are anhydrified on Na₂SO₄ and the solvent is evaporated. 14g of raw 4-methylene(2-indan-1-one)indene are obtained.

-   13.8 g of raw 4-methylene(2-indan-1-one)indene-   2.6 g (68.42 mmoles) of sodium borohydride-   120 ml of tetrahydrofuran-   60 ml of hexane.

NaBH₄ is added to the solution in THF and hexane of1-indanone-2-substituted, at −20° C. The mixture is left to rise to roomtemperature. After 2 hours water is added and the mixture is extractedwith ethyl ether. After washing the organic extracts to neutrality witha saturated aqueous solution of NH₄Cl and anhydrifying on Na₂SO₄, thesolvent is evaporated. 13.0 g of raw 4-methylene(2-indan-1-ol)indene areobtained.

-   13.0 g of raw 4-methylene(2-indan-1-ol)indene-   15.0 g of anhydrous copper sulfate-   100 ml of toluene.

The alcohol is added to the suspension of CuSO₄ in toluene. After 90minutes at 110° C. the mixture is poured into water and extracted withethyl ether. After washing the organic extracts to neutrality with waterand anhydrifying on Na₂SO₄, the solvent is evaporated. 1.8 g of4-methylene(2-indenyl)indene are obtained, after purification on asilica gel column (eluant: hexane/ethyl acetate=99/1).

EXAMPLE 5 Synthesis of1-methyl-4-methylene(1-η⁵-indenyl)-η⁵-indenyl)-η⁵-indenyl zirconiumdichloride

-   2.4 g (9.3 mmoles) of 1-methyl-4-methylene(1-indenyl)indene-   15 cc (24 mmoles) of LiBu 1.6 M in hexane-   80 cc of ethyl ether-   1.7 g (5.6 mmoles) of ZrCl₄.

LiBu is added, by means of a drip funnel, to the ether solution of1-methyl-4-methylene(1-indenyl)indene; approximately half-way throughthe addition the corresponding lithium salt begins to precipitate. Thesolution is dark yellow whereas the precipitate is white. The mixture isleft under stirring for a night. A DCI control (sample treated withmethyl iodide) shows the presence of ligand, mono-salt and di-salt, inapproximately equimolar quantities. A further 10 cc of LiBu are added.GC mass analysis reveals the presence of the di-salt with traces ofmono-salt and the absence of the ligand. The mixture is left understirring for 1 night.

The lithium salt is decanted, washed several times with hexane andfinally dried under vacuum. The solid is suspended in about 80 cc oftoluene, cooled to −70° C. and then zirconium tetrachloride is added.The temperature is left to rise spontaneously to room value and themixture is left under stirring for a further 30 minutes. The suspension(dark red) is filtered and washed with toluene (3×10 ml) andsubsequently with methylene chloride (3×10 ml).

The filtrate is concentrated, the formation of pitchy products isobserved, which are separated by filtration. The limpid solution isdried, and ethyl ether is added to the residue obtained. There is theinitial formation of a solution from which the complex is separated inthe form of a yellow solid.

¹H-NMR (ppm rel. to TMS).

-   7.50–7.15 (m, 4H), 7.13–6.90 (m, 3H), 6.73 (d, 1H, J=3.1 Hz), 6.63    (d, 2H, J=2.6 Hz), 6.54 (d, 1H, J=3.0 Hz), 4.53 (d, 1H, J=14.0 Hz),    4.32 (d, 1H, J=14.0 Hz), 2.44 (s, 3H).

EXAMPLES 6–9 Copolymerization of ethylene/propylene

Examples 6 to 9 refer to a series of copolymerization tests for thepreparation of elastomeric polymers of the EPR type based onethylene/propylene, carried out using a catalytic system comprising onthe one hand the metallocene complex 1-methyl-4methylene(1-η⁵-indenyl)-η⁵-indenyl zirconium dichloride, obtained as describedabove in example 5 and methylalumoxane (MAO) as cocatalyst. The specificpolymerization conditions of each example and the results obtained areindicated in Table 1 below, which specifies in succession, the referenceexample number, the quantity of zirconium used, the atomic ratio betweenaluminum in MAO and zirconium, the total polymerization pressure, theactivity of the catalytic system with reference to the zirconium, therelative quantity, by weight, of the C₃ monomeric units in the polymer,the weight average molecular weight M_(w) and the molecular weightdispersion M_(w)/M_(n).

The polymerization is carried out in a 0.5 liter pressure reactor,equipped with a magnetic anchor drag stirrer and an external jacketconnected to a heat exchanger for the temperature control. The reactoris previously flushed by maintaining under vacuum (0.1 Pascal) at atemperature of 80° C. for at least 2 h.

120 g of liquid “polymerization grade” propylene are fed into thereactor at 23° C. The reactor is then brought to the polymerizationtemperature of 40° C. and, “polymerization grade” gaseous ethylene isfed by means of a plunged pipe until the desired equilibrium pressure(2.0–2.7 MPa) is reached. Under these conditions the molar concentrationof ethylene in the liquid phase ranges from 11 to 23%, depending on thetotal pressure of the system, as can be easily calculated using theappropriate liquid-vapor tables.

MAO, as a 1.5 M solution (as Al) in toluene (commercial product Eurecene5100 10T of Witco) and the desired quantity of the above metallocenecomplex, as a toluene solution having a concentration generally rangingfrom 3×10⁻⁴ to 1×10⁻³ M, are charged into a suitable tailed test-tube,maintained under nitrogen. The catalyst solution thus formed ismaintained at room temperature for a few minutes and is then transferredunder a stream of inert gas to a metal container from which it isintroduced into the reactor, by means of an overpressure of nitrogen.

The polymerization reaction is carried out at 40° C., care being takenthat the total pressure is kept constant by continuously feedingethylene to compensate the part which has reacted in the meantime. After15 minutes the feeding of ethylene is interrupted and the polymerizationis stopped by the rapid degassing of the residual monomers. The polymeris recovered, after washing it with ethyl alcohol and drying at 60° C.,1000 Pa, for at least 8 h. The solid thus obtained is weighed and thecatalytic activity is calculated as kilograms of polymer per gram ofmetal zirconium per hour: (kg_(pol)./g_(zr)xh). The content of thepropylene units is measured on the dried and homogenized solid, by meansof the known techniques based on IR spectroscopy, together with theweight (Mw) and number (M_(n)) average molecular weight. The results areindicated in Table 1.

EXAMPLES 10–12

Examples 10 to 12 refer to a series of copolymerization tests for thepreparation of elastomeric polymers of the EPR type based onethylene/propylene using a catalytic system comprising the metallocenecomplex, obtained as described above in example 5, an aluminum alkyl andan appropriate compound of boron as cocatalyst.

The procedure described in examples 6–9 is followed with the followingvariations:

About 120 g of “polymerization grade” liquid propylene and the exactquantity of Al(iso-Bu)₃ are fed into the reactor at 23° C., so as toobtain a concentration of aluminum equal to 5×10⁻³ moles/liter. Thereactor is then brought to the polymerization temperature of 40° C. and“polymerization grade” gaseous ethylene is fed by means of a plungedpipe, until the desired equilibrium pressure (2.2–2.7 MPa) is reached.Under these conditions the molar concentration of ethylene in the liquidphase ranges from 12 to 23%, depending on the total pressure of thesystem, as can be easily calculated using the appropriate liquid-vaportables.

Al(iso-Bu)₃ as an 0.4 M solution in toluene and the desired quantity ofmetallocene complex, prepared as described in example 5, as a toluenesolution having a concentration generally ranging from 3×10⁻⁴ to 1×10⁻³M, are charged into a suitable tailed test-tube, maintained undernitrogen. The solution thus obtained is maintained under stirring at 23°C. for 15 minutes after which a toluene solution, having a concentrationgenerally ranging from 5×10⁻⁴ to 1×10⁻³ M, of [CPh₃][B(C₆F₅)₄] is addedand, after a few minutes, it is transferred under a stream of inert gasto a metal container from which it is introduced into the reactor, bymeans of an overpressure of nitrogen. The results are indicated in Table2.

TABLE 1 C₂/C₃ copolymerization tests with a catalytic system composed of1-methyl-4- methylene(1-η⁵-indenyl)-η⁵-indenyl zirconium dichloride andMAO Example Zr Al/Zr P_(total) Activity C_(3(polymer)) M_(w) Nr. (moles× 10⁶) (mol/mol) (MPa) (kg_(pol.)/g_(Zr) × h) (weight %) (× 10³)M_(w)/M_(n) 6 1.75 1975 2.0  218 62  89 2.8 7 1.30 2385 2.2  806 55 1342.9 8 0.65 3950 2.5 3275 44 208 2.4 9 0.38 5980 2.7 6070 39 317 2.2

TABLE 2 C₂/C₃ copolymerization tests carried out using the catalyticsystem composed of 1- methyl-4-methylene(1-η⁵-indenyl)-η⁵-indenylzirconium dichloride, Al(iso-Bu)₃ and CPh₃[B(C₆F₅)₄]. Example Zr Al/ZrB/Zr P_(total) Activity C_(3(polymer)) M_(w) Nr. (moles × 10⁶) (mol/mol)(mol/mol) (MPa) (kg_(pol.)/g_(Zr) × h) (weight %) (× 10³) M_(w)/M_(n) 101.1 350 1.1 2.2  567 48 162 3.1 11 0.9 350 1.1 2.5 1758 41 237 2.6 120.6 350 1.1 2.7 2749 35 330 2.4

1. A metallocene compound having formula (I):

wherein: R₁ and R₂ can independently occupy any of the free positions ofthe indene group; R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ independentlyrepresent hydrogen, halogen, a linear or branched, saturated orunsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbyl group, or aC₁–C₂₀ hydrocarbyl group substituted with one or more halogen atoms, ora C₁–C₂₀ hydrocarbyl group comprising one or more heteroatoms of groups14 to 16 of the periodic table of elements; wherein any two, or bothpairs, of the substituents R₃, R₄, R₅ and R₆, adjacent to each other,may be joined to each other to form a saturated or unsaturated C₄–C₂₀cyclic structure, comprising a bond of the cyclopentadienyl ring, saidstructure optionally containing one or more heteroatoms; M representstitanium, zirconium or hafnium; X₁ and X₂ each independently representan anionic group bound to the metal M, wherein X₁ and X₂ may bechemically bound to each other to form a cycle having from 4 to 7 atomsdifferent from hydrogen, also comprising the metal M.
 2. The metallocenecompound of claim 1, wherein the halogen is selected from the groupconsisting of F, Cl and Br.
 3. The metallocene compound of claim 1,wherein the heteroatom is selected from the group consisting of Si, O,N, S and P.
 4. A metallocene compound having formula (I),

wherein R₁ and R₂ can independently occupy any of the free positions ofthe indene group; R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ independentlyrepresent hydrogen, halogen, a linear or branched, saturated orunsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbyl group, or aC₁–C₂₀ hydrocarbyl group substituted with one or more halogen atoms, ora C₁–C₂₀ hydrocarbyl group comprising one or more heteroatoms of groups14 to 16 of the periodic table of elements; wherein any two, or bothpairs, of the substituents R₃, R₄, R₅ and R₆, adjacent to each other,may be joined to each other to form a saturated or unsaturated C₄–C₂₀cyclic structure, comprising a bond of the cyclopentadienyl ring, saidstructure optionally containing one or more heteroatoms; M representstitanium, zirconium or hafnium; X₁ and X₂ each independently representan anionic group bound to the metal M, wherein X₁ and X₂ may bechemically bound to each other to form a cycle having from 4 to 7 atomsdifferent from hydrogen, also comprising the metal M, wherein groups X₁and X₂ are selected from chloride, methyl, ethyl, butyl, isopropyl,isoamyl, octyl, decyl, benzyl, allyl, methylallyl, cyclopentyl,cyclohexyl, 4-methylcyclohexyl, phenyl, toluyl, methoxyl, ethoxyl,iso-butoxyl, sec-butoxyl, ethylsulfide, acetate, propionate, butyrate,pivalate, versatate, naphthenate, diethylamide, dibutylamide, orbis(trimethylsilyl)amide; or wherein X₁ and X₂ are chemically bound toeach other to form one or more divalent anionic groups.
 5. Themetallocene compound of claim 4, wherein the divalent anionic group is atrimethylene, tetramethylene or ethylenedioxy group.
 6. The metallocenecompound of claim 4, wherein the halogen is selected from the groupconsisting of F, Cl and Br.
 7. The metallocene compound of claim 4,wherein the heteroatom is selected from the group consisting of Si, O,N, S and P.
 8. A compound having formula (Ia):

wherein: R₁ and R₂ can independently occupy any of the free positions ofthe indene group; R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ independentlyrepresent hydrogen, halogen, a linear or branched, saturated orunsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbyl group, or aC₁–C₂₀ hydrocarbyl group substituted with one or more halogen atoms, ora C₁–C₂₀ hydrocarbyl group comprising one or more heteroatoms of groups14 to 16 of the periodic table of elements, wherein any two, or bothpairs, of the substituents R₃, R₄, R₅ and R₆, adjacent to each other,may be joined to each other to form a saturated or unsaturated C₄–C₂₀cyclic structure, comprising a bond of the cyclopentadienyl ring, saidstructure optionally containing one or more heteroatoms.
 9. The compoundaccording to claim 8, selected from the group consisting of:


10. The compound of claim 8, wherein the halogen is selected from thegroup consisting of F, Cl and Br.
 11. The metallocene compound of claim8, wherein the heteroatom of Groups 14–16 of the periodic table of theelements is selected from the group consisting of Si, O, N, S and P. 12.A process for the preparation of the compound (Ia) comprising,

(a) reaction of 1-indanol derivatives having formula (II), with LiBu togive the double salt having formula (III);

wherein R₁ and R₂ can independently occupy any of the free positions ofthe indene group, and R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ mayindependently represent hydrogen, halogen, a linear or branched,saturated or unsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbylgroup, or a C₁–C₂₀ hydrocarbyl group substituted with one or morehalogen atoms, or a C₁–C₂₀ hydrocarbyl group comprising one or moreheteroatoms of groups 14 to 16 of the periodic table of elements,wherein any two, or both pairs, of the substituents R₃, R₄, R₅ and R₆,adjacent to each other, may be joined to each other to form a saturatedor unsaturated C₄–C₂₀ cyclic structure, comprising a bond of thecyclopentadienyl ring, said structure optionally containing one or moreheteroatoms; (b) reaction of the double lithium salt having formula(III), obtained in (a), with one or more electrophilic reagents, toobtain hydroxy ester (IV);

(c) dehydration reaction of the alcohol function of the hydroxy ester(IV), obtained in (b), carried out in an acid environment to give theester (V);

(d) reduction reaction of the ester having formula (V), obtained in (c),with the formation of alcohol (VI):

(e) bromination reaction of the alcohol having formula (VI) to give thebromine derivative (VII);

(f) formation reaction of the indenyl cyclopentadienyl derivative havingformula (Ia), starting from the bromine derivative having formula (VII)obtained in (e) and from cyclopentadienyl anions, whose correspondingneutral derivative can be represented by the following formula (VIII)

.
 13. The process according to claim 12, wherein: (a) is carried out inan organic solvent, in the presence of one or more base reagents and attemperatures of from −30° to 120° C.; (b) is carried out in the presenceof hydrocarbon and/or ether solvents or mixtures thereof at temperaturesof from −100° to 120° C.; (c) is carried out in the presence of asolvent and a strong acid at temperatures of from −25° to 150° C. (d) iscarried out in an organic solvent, with a reagent selected from thegroup consisting of LiAlH₄, NaBH₄, NaH, MgH₂, LiBu, LiMe, MeMgCl,PhMgBr, and Bu^(t)MgCl at temperatures of from −70° to 100° C; (e) iscarried out in an organic solvent by means of a brominating agent; (f)is carried out in a solvent selected from the group consisting ofaromatic hydrocarbons, aliphatic hydrocarbons, ethers and mixturesthereof, at a temperature of from −80° to 120° C. and thecyclopentadienyl anion is obtained by the reaction of the correspondingneutral derivative, having formula (VIII), with a reagent selected fromthe group consisting of alkyls of electro-positive metals, hydrides ofelectro-positive metals, Grignard reagents, alkaline metals,earth-alkaline metals and alloys of alkaline and earth-alkaline metals,in a solvent selected from the group consisting of aliphatichydrocarbons, aromatic hydrocarbons, ethers and mixtures thereof, attemperatures of from −80° to 110°C.
 14. The process according to claim13, wherein: (a) is carried out in hexane as solvent, in the presence oflithium butyl at temperatures of from 0° to 70° C.; (b) is carried outin hexane as solvent at temperatures of from −70° to 25° C.; (c) iscarried out in toluene as solvent in the presence ofpara-toluenesulfonic acid, at temperatures of from 50 to 110° C. (d) iscarried out in ethyl ether, in the presence of LiAlH₄, at temperaturesof from −30° to 25° C.; (e) is carried out in methylene chloride in thepresence of PBr₃ at temperatures of from −20° to 25° C.; (f) thecyclopentadienyl anion is obtained by the reaction between indene or4,7-dimethyl-indene, with lithium butyl, in mixtures of hexane/THF attemperatures of from 0° to 60° C.
 15. The process of claim 13, whereinthe strong acid is selected from the group consisting of HCl, H₂SO₄,para-toluenesulfonic acid and a blander dehydrating agent.
 16. Theprocess of claim 15, wherein the blander dehydrating agent is a silicagel.
 17. The process according to claim 12, wherein (f) is carried outby reacting the brominated product (VII) with a lithium enolate to formone or more indenyl-cyclopentadienyl products having formula (XIII):

wherein: R₁ and R₂ can independently occupy any of the free positions ofthe indenyl group; R₁, R₂, R₇, R₈, R₉, R₁₀, and R₁₁ independentlyrepresent hydrogen, halogen, a linear or branched, saturated orunsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbyl group, or aC₁–C₂₀ hydrocarbyl group substituted with one or more halogen atoms, ora C₁–C₂₀ hydrocarbyl group comprising one or more heteroatoms of groups14 to 16 of the periodic table of elements; or, wherein any two of thesubstituents R₉, R₁₀ and R₁₁, adjacent to each other, may be joined toeach other to form a saturated or unsaturated C₄–C₂₀ cyclic structure,comprising a bond of the cyclopentadienyl ring, said structureoptionally containing one or more heteroatoms; R₁₂ can be independentlyhydrogen, a linear or branched, saturated or unsaturated, cycloaliphaticor aromatic C₁–C₂₀ hydrocarbyl group, or a C₁–C₂₀ hydrocarbyl groupcomprising one or more heteroatoms of groups 14 to 16 of the periodictable of elements; said process further comprising (g) reaction of acyclic ketone having formula (IX), with a lithium amide to form amixture of one or more anions having formula (Xa)/(Xb);

(h) reaction of the mixture of anions (Xa)/(Xb) with the brominatedproduct having formula (VII), prepared according to (g) to form (XI);

(i) reduction of the functional carbonyl group to alcohol with theformation of the derivative having formula (XII),

(j) dehydration of the derivative having formula (XII), obtained in (i),with the formation of the indenyl-cyclopentadienyl compound, havingformula (XIII).
 18. The process of claim 17, wherein the halogen isselected from the group consisting of F, Cl and Br.
 19. The process ofclaim 17, wherein the heteroatom is selected from the group consistingof Si, O, N, S and P.
 20. The process of claim 12, wherein theelectrophilic reagent is diethyl carbonate.
 21. The process of claim 12,wherein the halogen is selected from the group consisting of F, Cl andBr.
 22. The process of claim 12, wherein the heteroatom is selected fromthe group consisting of Si, O, N, S and P.
 23. The process according toclaim 12, wherein the cyclopentadienyl anion is obtained by the reactionof the corresponding neutral derivative, having formula (VIII), with areagent selected from the group consisting of alkyls of lithium, lithiumhydride and lithium metal.
 24. A catalyst for the polymerization ofolefins comprising a reaction product between: (A) one or moremetallocene compounds having formula (I), free or supported on inertsolids; and

(B) one or more compounds capable of forming a metallocene alkyl cation,wherein: R₁ and R₂ can independently occupy any of the free positions ofthe indene group; R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ independentlyrepresent hydrogen, halogen, a linear or branched, saturated orunsaturated, cycloaliphatic or aromatic C₁–C₂₀ hydrocarbyl group, or aC₁–C₂₀ hydrocarbyl group substituted with one or more halogen atoms, ora C₁–C₂₀ hydrocarbyl group comprising one or more heteroatoms of groups14 to 16 of the periodic table of elements; wherein any two, or bothpairs, of the substituents R₃, R₄, R₅ and R₆, adjacent to each other,may be joined to each other to form a saturated or unsaturated C₄–C₂₀cyclic structure, comprising a bond of the cyclopentadienyl ring, saidstructure optionally containing one or more heteroatoms; M representstitanium, zirconium or hafnium; X₁ and X₂ each independently representan anionic group bound to the metal M, wherein X₁ and X₂ may bechemically bound to each other to form a cycle having from 4 to 7 atomsdifferent from hydrogen, also comprising the metal M.
 25. The catalystfor the polymerization of olefins according to claim 24, wherein thecompound B is an aluminoxane.
 26. The catalyst of claim 24, wherein thehalogen is selected from the group consisting of F, Cl and Br.
 27. Thecatalyst of claim 24, wherein the heteroatom is selected from the groupconsisting of Si, O, N, S and P.
 28. A process for the preparation ofthe catalyst according to claim 24, comprising contacting the components(A) and (B) with each other at temperatures of from 20° to 60° C. andfor times from 10 seconds to 1 hour, in a hydrocarbon medium and in aproportion that the atomic ratio between the aluminum in the aluminoxaneand the transition metal M is within the range of 10 to
 10000. 29. Theprocess of claim 25, wherein the atomic ratio between the aluminum inthe alumoxane and the transition metal M is from 100 to 5,000.
 30. Aprocess for the polymerization of olefins, comprising polymerizing oneor more olefinic monomers in the presence of the catalyst as defined inclaim
 25. 31. The process according to claim 30, wherein one or moreolefinic monomers are polymerized in the presence of a metallocenehaving formula (I) and methylalumoxane (MAO) as a cocatalyst.
 32. Theprocess according to claim 31, wherein the olefinic monomers arepolymerized in the presence of a metallocene having formula (I), analuminum alkyl and a boron compound as a cocatalyst.
 33. The processaccording to claim 32, wherein the olefinic monomers are selected fromthe group consisting of ethylene, propylene and mixtures thereof. 34.The process of claim 31, wherein the olefinic monomers are selected fromthe group consisting of ethylene, propylene and mixtures thereof.